JPH0783084A - Hydraulic construction machinery - Google Patents

Abstract

(57) [Summary] [Purpose] Good for work requiring a large amount of pump flow at low load without increasing the capacity of the variable displacement hydraulic pump or setting the engine speed higher during normal work. To provide a hydraulic construction machine that can perform. An engine 27, a rotation control device 28 for the engine, a variable displacement hydraulic pump 1 driven by the engine, a regulator 44 for setting an input torque of the hydraulic pump, and a discharge from the variable displacement hydraulic pump. It is applied to a hydraulic construction machine equipped with actuators 4 and 21 driven by pressure oil. The controller 50 includes a first mode in which a first engine speed and a first pump input torque are combined, a second engine speed higher than the first engine speed, and the first pump input torque. The second mode is set in combination with the second pump input torque smaller than the above. When performing work requiring a large pump flow rate at low load, the mode selection switch 58 selects the second mode, and during other normal work, the mode selection switch selects the first mode. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic construction machine such as a hydraulic excavator, and more particularly to a drive control device for an engine and a variable displacement hydraulic pump mounted on the hydraulic construction machine.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Laid-Open No. 62-2334.
No. 30, JP-B 3-29559, JP-A-62.
As described in Japanese Patent Publication No. 58033, etc., in a hydraulic construction machine such as a hydraulic excavator, in order to obtain an optimum engine output characteristic or a variable displacement hydraulic pump discharge characteristic in accordance with various traveling conditions and working conditions, A drive control device has been proposed.

The one disclosed in Japanese Patent Laid-Open No. 62-233430 has a first maximum fuel injection having an engine output characteristic suitable for work in order to optimize the engine output characteristic at the time of work such as excavation and traveling. Amount and a second maximum fuel injection amount having an engine output characteristic suitable for traveling are stored in advance, and when the construction machine is in a working state, the first maximum fuel injection amount is set as an engine rotation speed. Based on this, the maximum injection amount set in advance is selected, and when the vehicle is traveling, the second maximum fuel injection amount is selected as the maximum injection amount.

The technique disclosed in Japanese Utility Model Publication No. 3-29559 requires a large amount of work at the time of heavy excavation and the like. In order to reduce the fuel consumption rate, noise, etc. at times, etc., a first maximum rotation speed that is predetermined based on heavy work among a plurality of maximum rotation speeds of the prime mover that is set based on the type of work, and The first combination with the maximum tilt angle of the variable displacement hydraulic pump in the range that does not exceed the output torque at the maximum rotation speed of 1.
And a second maximum rotation speed smaller than the first maximum rotation speed that is predetermined based on light work among the plurality of maximum rotation speeds and an output of the second maximum rotation speed. A second mode in which a second maximum tilt angle that is larger than the first maximum tilt angle that is predetermined among a plurality of maximum tilt angles of the variable displacement hydraulic pump that does not exceed the torque is combined is set. Setting means for setting is provided, and the prime mover is selectively driven according to the set value set by the setting means to control the discharge amount of the variable displacement hydraulic pump.

The one disclosed in Japanese Patent Laid-Open No. 62-58033 is further divided into modes as compared with the second example, and the operator is selected according to each state of high speed running, low speed running, heavy work and light work. Which is capable of operating the actuating body, and is configured to change the maximum rotation speed changing means of the prime mover, the maximum discharge volume changing means of the variable displacement hydraulic pump, and one of a plurality of maximum rotation speeds that can be changed. One of a plurality of possible maximum discharge volumes is associated with one set, and a plurality of sets are set in advance, and one of the plurality of sets is selected according to the operation form of the actuating body. The setting / selecting means, the instructing means for instructing the target operation form of the actuating body, and the detecting means for detecting whether or not the actuator is in the operating state, are output from the instructing means and the detecting means. To the signal It is obtained so as to drive the maximum rotational speed changing unit and the maximum discharge volume varying means in response to the selected value by the setting-selecting means Zui.

[0006]

By the way, among the works performed by the construction machine, for example, a bucket cloud (work of pulling the bucket toward you) or a work of crushing rocks or the like performed by mounting a crusher on the work machine. Some work requires a large amount of pump flow when the load is low. However, this point is not considered at all in the above-mentioned known example, and in order to realize such work, it is necessary to mount a large capacity pump or set a high engine speed. . If a large-capacity pump is installed, the cost of construction machinery will increase, and if the engine speed is set high, during normal work (work other than work requiring a large amount of pump flow at low load and running), Various problems such as increase of fuel consumption rate, deterioration of heat balance, and increase of noise occur.

The present invention has been made to solve the inconveniences of the prior art, and its object is to increase the capacity of the variable displacement hydraulic pump or to set the engine speed higher during normal work. It is an object of the present invention to provide a hydraulic construction machine that can satisfactorily perform work that requires a large amount of pump flow without load.

[0008]

In order to achieve the above object, the present invention provides an engine, a rotation control device for controlling the rotation speed of the engine, a variable displacement hydraulic pump driven by the engine, A hydraulic construction machine equipped with a regulator for setting an input torque of the variable displacement hydraulic pump and an actuator driven by pressure oil discharged from the variable displacement hydraulic pump, comprising: a first engine speed and a first pump; The first mode in which the input torque is combined is set, and the second engine speed higher than the first engine speed and the second pump input torque smaller than the first pump input torque are set. Mode setting means for setting a combined second mode, and the first mode or the second mode set in the mode setting means.
And a mode selecting means for outputting an engine speed signal and a pump input torque signal according to the selected mode.

The above-mentioned mode selecting means is used for the second operation when performing a work requiring a large pump discharge flow rate at a low load.
Select the mode of above, and in the other normal work,
Can be selected. Regarding the selection of each mode, a work detecting means for separately detecting a work requiring a large pump discharge flow rate at a low load is provided separately,
The mode selecting means may be configured to automatically select either the first mode or the second mode in response to a signal from the work detecting means, and a mode operated by an operator. A selection switch may be separately provided, and the mode selection means may manually select either the first mode or the second mode in response to a signal from the mode selection switch.

Further, the hydraulic construction machine is provided with a target rotation speed setting means for setting a target rotation speed of the engine and an operation amount detecting means for detecting an operation amount of the target rotation speed setting means. The number of revolutions may be controlled in accordance with the operation amount detection signal with each characteristic corresponding to the first mode or the second mode. Also,
Target rotation speed detection means for detecting the target rotation speed of the engine, actual rotation speed detection means for detecting the actual engine rotation speed, according to the rotation speed deviation between the target rotation speed and the actual rotation speed,
A correction means for correcting the pump input torque may be provided, and the correction amount of the pump input torque may be changed according to the first mode or the second mode.
In this case, both the first mode and the second mode can be set in the mode setting means so that the pump input torque becomes small in a region where the target engine speed is equal to or higher than a predetermined engine speed. . Further, in these cases, the pump input torque can be set in the mode setting means within a range that does not exceed the output torque of the engine corresponding to the target rotation speed of the engine.

Further, in these hydraulic construction machines,
The input horsepower of the variable displacement hydraulic pump when the first mode is selected in the mode setting means, and the second horsepower
The engine speed and the pump input torque can be set so that the input horsepower of the variable displacement hydraulic pump when the mode is selected becomes substantially equal.

[0012]

As shown in FIG. 7, the engine mounted on the construction machine generally has a large output torque in the medium speed rotation range and a smaller output torque as the rotation speed increases. On the other hand, as shown in the figure, the fuel consumption rate is good in the medium speed rotation range and becomes worse as the rotation speed becomes higher. Further, an RSV governor for controlling the engine speed is usually attached to the engine mounted on the construction machine. However, in such an engine, the governor lever position (the target engine speed) is set because of the characteristics of the RSV governor. When it is kept constant, the fuel consumption rate deteriorates as the load (input torque of the variable displacement hydraulic pump) decreases. Generally, the horsepower of an engine mounted on a construction machine is set in consideration of the work load, the front strength, the heat balance, etc. of the construction machine, but as long as the engine output horsepower corresponding to the required work quantity is obtained. For example, it is preferable to reduce the engine speed as much as possible in order to improve the fuel consumption rate and heat balance, and reduce noise.

Since the output horsepower P of the engine is a constant, T is the input torque of the variable displacement hydraulic pump, and N is the engine speed, there is a relationship of P = C.TN.N, so the engine speed N Even if is lowered, a constant horsepower P can be secured by increasing the input torque T of the variable displacement hydraulic pump. In the example of FIG. 7, the input torques T ₁ and T ₂ (T ₁ > T ₂ ) of the variable displacement hydraulic pump and the engine speeds N ₁ and N ₂ (N
_By setting ₁ <N ₂ ) such that P ₀ = C · T ₁ · N ₁ = C · T ₂ · N ₂ , the desired engine speed can be reduced from N ₂ to N ₁ . The engine horsepower P ₀ can be secured. However, if the engine speed is reduced, the
As indicated by the characteristic line A, the pump flow rate at low load is smaller than that when the engine speed is increased (characteristic line B in FIG. 8).

However, during normal work, if a desired work amount can be secured, the pump flow rate under a low load is sufficient. Therefore, during normal work, the first engine that combines a low engine speed and a large pump input torque is used.
Mode is assigned to control the engine speed and pump input torque by assigning a second mode that combines high engine speed and small pump input torque during crushing work that requires a large pump flow rate at low load. By doing so, it is possible to perform work such as crushing that requires a large pump flow rate at low load, without increasing the capacity of the variable displacement pump or setting the engine speed at a high level during normal work. Therefore, it is possible to provide a multifunctional and high-performance construction machine at low cost, improve the fuel consumption rate during normal work, and reduce the amount of heat released to the engine cooling water as the fuel consumption rate improves. It is possible to improve the heat balance, and further, it is possible to reduce noise as the engine speed decreases.

[0015]

Embodiments <First Embodiment> A first embodiment of the present invention will be described with reference to FIGS. The hydraulic construction machine according to the first embodiment controls the pump input torque within a range that does not exceed the output torque corresponding to the engine speed according to the selected mode signal,
The feature is that the control amount of so-called speed sensing is changed.

FIG. 1 is a block diagram of a hydraulic construction machine according to this embodiment, in which 1 is a variable displacement hydraulic pump, and 27 is an engine for driving this variable displacement hydraulic pump. Engine 2
The rotation speed of 7 is controlled by rotating the governor lever 27b of the governor 27a by the pulse motor 28. Then, the discharge oil of the variable displacement hydraulic pump 1 according to the engine speed is guided to the traveling hydraulic motor 4 via the traveling control valve 2 and to the working hydraulic cylinder 21 via the working control valve 20. Be guided.

This hydraulic construction machine is equipped with a forward / reverse switching valve (not shown), a pilot valve operated by a pedal, and a pilot hydraulic pump. For example, the forward / backward switching valve is switched to forward and the pedal of the pilot valve is changed. When operated, the oil discharged from the pilot hydraulic pump is guided to the pilot port 2a of the hydraulic pilot type traveling control valve 2, and the traveling control valve 2 is switched by the stroke amount according to the pilot hydraulic pressure. As a result, the oil discharged from the variable displacement hydraulic pump 1 is supplied to the traveling hydraulic motor 4 via the conduit 91, the pressure compensation valve 23, and the traveling control valve 2, and the vehicle travels. The speed of the vehicle depends on the depression amount of the pedal.

Further, this hydraulic construction machine is provided with a slow return valve (not shown). When the pedal is released during traveling, the pilot valve shuts off the pressure oil, and its outlet port communicates with the tank. As a result, pilot port 2
The pressure oil acting on a returns to the tank via the forward / reverse switching valve, the slow return valve, and the pilot valve. At this time, the return oil is throttled by the throttle of the slow return valve,
The vehicle is gradually decelerated while the pilot control valve 2 is gradually switched to the neutral position.

Further, this hydraulic construction machine is provided with a work lever and a pressure reducing valve (not shown). When the work lever is operated, the pressure reduced by the pressure reducing valve according to the operation amount of the work lever is used for the hydraulic pilot type work. The control valve 20 is switched, and the discharge oil from the variable displacement hydraulic pump 1 is guided to the work hydraulic cylinder 21 via the pipe line 92, the pressure compensation valve 24 and the control valve 20, and the work hydraulic cylinder 21 expands and contracts. A work attachment such as a boom moves up and down. Here, the pressure compensating valves 23 and 24 independently compensate the operations of the traveling hydraulic motor 4 and the working hydraulic cylinder 21, and apply a pressure higher than the respective load pressure by a predetermined pressure to the variable displacement hydraulic pump 1. It is intended to be supplied.

The tilt angle of the variable displacement hydraulic pump 1, that is, the displacement volume, is controlled by a regulator such as a tilt angle control device 4.
Controlled by 0. The tilt angle control device 40 controls the piston position by the hydraulic pump 41 driven by the engine 27, the pair of electromagnetic valves 42, 43, and the pressure oil from the hydraulic pump 41 according to the switching of the electromagnetic valves 42, 43. The tilt angle of the variable displacement hydraulic pump 1 is controlled according to the piston position of the servo cylinder 44. Here, the pair of solenoid valves 42 and 43 is switch-controlled by the controller 50.

Reference numeral 51 in the figure denotes a variable displacement hydraulic pump 1.
Of the tilt angle θs of the variable displacement hydraulic pump 1, 52 is a pressure sensor for detecting the discharge pressure Pp of the variable displacement hydraulic pump 1,
3 is a rotation speed sensor for detecting the rotation speed Nr of the engine 27, 54 is the discharge pressure of the variable displacement hydraulic pump 1 and the maximum load pressure of the actuator (of the load pressure of the variable displacement hydraulic pump 1 and the load pressure of the hydraulic cylinder 21). It is a larger value and is a differential pressure sensor for detecting a differential pressure with respect to the one selected by the shuttle valve 29, that is, a load sensing differential pressure (hereinafter, LS differential pressure) ΔPLS. Also, 55
Is a potentiometer that detects the amount of rotation (control speed) Nθ of the governor lever 27b, and the detection results of these sensors are input to the controller 50. Reference numeral 57 is a rotation speed setting device for instructing a rotation speed X in accordance with a manual operation of the fuel lever 57a.
Entered in. Further, reference numeral 58 is a mode selection means, for example, a mode selection switch, which requires a combination of the engine speed and the pump input torque in a first mode suitable for normal work and a large pump flow rate at low load such as crushing work. Switch to the second mode suitable for the work to be performed. The first mode is a combination of low engine speed and high pump input torque, and the second mode is a combination of high engine speed and low pump input torque. This point will be described later in more detail with reference to FIGS. 3 and 4. The state of the mode selection switch 58 is also input to the controller 50.

The controller 50 is provided with a tilt angle control circuit 60 for controlling the pump tilt angle as shown in FIG. The control circuit 60 includes a load sensing control unit (hereinafter, LS control unit) 61 and a torque control unit 10.
0, a minimum value selection unit 63, and a servo control unit 64.

The LS controller 61 controls the target differential pressure ΔPLSR.
And a deviation Δ (PLS) from the LS differential pressure ΔPLS detected by the differential pressure sensor 54, and a deviation ΔθL of the target value is calculated from the deviation Δ (PLS), which is integrated to perform load sensing control. The target pump tilt angle θL for is calculated and output.

The torque control unit 100 determines the target torque Tpo.
Of the target torque calculation unit 101 and the target torque Tpo calculated by the target torque calculation unit 101.
The target for input torque control is calculated by multiplying the reciprocal of the pump discharge pressure Pp detected in 2 to perform tilt angle calculation, and the value θps obtained by the calculation unit 102 is filtered by a first-order lag element. It has a tilt angle calculation unit 103 for obtaining a pump tilt angle θT. The target torque calculation unit 10
1 is the engine speed N detected by the speed sensor 53
The correction torque ΔT is calculated from the deviation between r and the governor lever position (control speed) Nθ detected by the potentiometer 55 to perform speed sensing, and the target torque Tpo for preventing engine stall is calculated from this deviation ΔT. .

FIG. 3 shows details of the target torque calculation unit 101. As shown in the figure, the target torque calculation unit 101 of this example includes four function generators 101a to 101d.
And two switching devices 101e and 101f and a deviation device 101
g, a correction torque calculation unit 101h, and an adder 101i.

The above four function generators 101a to 101d
The governor lever position Nθ of the prime mover detected by the potentiometer 55 is input to each. The first function generator 101a outputs a _first target torque Tr ₁ having the illustrated characteristic according to the input governor lever position Nθ. On the other hand, when the input governor lever position Nθ becomes a predetermined value or more, the second function generator 101b causes the first target torque Tr
The second target torque Tr ₂ larger than ₁ is output. In addition, the third function generator 101c outputs the _first reference rotation speed Ns ₁ having the illustrated characteristics according to the input governor lever position Nθ. On the other hand, the fourth function generator 101d sets the second reference rotation speed Ns ₂ which is always larger than the first reference rotation speed Ns ₁ as shown in the figure in accordance with the input governor lever position Nθ. Output.

First switch 101e and second switch 1
01f is switched to the contact a side when the mode selection switch 58 is switched to the first mode side suitable for normal work, and the mode selection switch 58 is required to have a large pump flow rate at a low load such as crushing work. When switched to the second mode side suitable for the work to be performed, both are switched to the contact b side. Therefore, when the mode selection switch 58 is switched to the first mode side, the second target torque Tr ₂ from the second function generator 101b and the second reference rotation from the fourth function generator 101d. The combination with the number Ns ₂ is the first switch 101e and the second switch 101f.
When the mode selection switch 58 is switched to the second mode side, the first target torque Tr ₁ from the first function generator 101a and the first target torque Tr ₁ from the third function generator 101c. The combination with the reference rotation speed Ns ₁ of is obtained from the first switching device 101e and the second switching device 101f.

The deviation device 101g is the second switching device 10 described above.
The deviation ΔN (Nr− between the first reference speed Ns ₁ or the second reference speed Ns ₂ selected by 1f and the actual engine speed Nr detected by the speed sensor 53.
Ns ₁ or Nr-Ns ₂₎ Request. Correction torque calculation unit 1
01h calculates the correction torque ΔT from the characteristic shown in the figure according to the rotation speed deviation ΔN. According to this characteristic, the correction torque becomes positive when the rotation speed deviation ΔN is positive, the correction torque becomes negative when the rotation speed deviation ΔN is negative, and |
The correction torque | ΔT | increases as ΔN | increases.

The adder 101i is the first switching device 10 described above.
The correction torque calculation unit 101h is added to the first target torque Tr ₁ or the second target torque Tr ₂ selected by 1e.
The correction torque ΔT obtained in step S1 is added, and the value is output as the target torque command value Tpo. The above is the configuration of the target torque calculation unit 101. And, as mentioned above,
The calculation unit 102 multiplies the target torque command value Tpo by the reciprocal of the pump discharge pressure Pp detected by the pressure sensor 52 to calculate the tilt angle, and the tilt angle calculation unit 103 outputs the tilt angle from the calculation unit 102. The target pump tilt angle θ for input torque control is obtained by filtering the value θps with a first-order lag element.
T is required.

Further, in FIG. 2, the minimum value selection unit 63
Selects the smaller one of the two target tilt angles θL and θT from the LS controller 61 and the torque controller 100 as the tilt angle command value θr, and outputs it to the servo controller 64. The servo control unit 64 uses the selected tilt angle command value θr.
Is compared with the tilt angle feedback value θs detected by the tilt angle sensor 51, and the solenoid valve 42 of the tilt angle control device 40 is controlled so that the pump tilt angle θs matches the tilt angle command value θr. Control 43.

Here, according to the load sensing control by the LS control section 61, the displacement volume of the variable displacement hydraulic pump 1 is controlled so that the LS differential pressure becomes a constant value, and the pump pressure is less than the load sensing pressure. Is also kept high by a predetermined target value, the pump discharge flow rate is controlled by the control valve 2 or
The pump tilt angle is controlled so that the required flow rate is 0, an excessive flow rate is not discharged, waste due to throttle loss is eliminated, and fuel efficiency and operability can be improved. Further, according to the input torque control by the torque control unit 100, the torque of the variable displacement hydraulic pump 1 is maintained within the range of the output torque of the engine 27, and the engine 27 is prevented from being overloaded.

Further, the controller 50 is provided with an engine speed control circuit 70 for controlling the engine speed shown in FIG. As shown in the figure, the engine speed control circuit 70 of this example includes three function generators 7.
1, 72, 78, a switching device 74, and a deviation device 77.

The function generators 71, 72 are provided with a rotation speed command value (fuel lever 57) sent from the rotation speed setting device 57.
The operation amount of a) X is input. The first function generator 71 outputs a _first target rotational speed Nx ₁ having the illustrated characteristic according to the input operation amount X of the fuel lever 57a. On the other hand, when the input operation amount X of the fuel lever 57a becomes equal to or larger than a predetermined value, the second function generator 72 causes the first target rotation speed N to be as shown in the figure.
A second target rotation speed Nx ₂ lower than x ₁ is output.

The selector 74 is switched to the contact a side when the mode selection switch 58 is switched to the first mode side suitable for normal work, and the mode selection switch 58 is operated at a large pump flow rate at a low load such as crushing work. Is switched to the contact b side when switched to the second mode side suitable for the required work. Therefore, when the mode selection switch 58 is switched to the side of the first mode, the second target rotation speed Nx ₂ is taken out from the switch 74 from the second function generator 72, and the mode selection switch 58 is switched to the above. When switched to the second mode side, the first function generator 7
From 1 to the first target rotational speed Nx ₁ is taken out from the switch 74.

The deviation device 77 is provided with the first target rotation speed Nx ₁ or the second target rotation speed N extracted from the switch 74.
The deviation between x ₂ and the governor lever position Nθ is calculated. Third
The function generator 78 of the
When N is equal to or greater than the predetermined value on the positive side, the pulse motor 28 is supplied with a signal in the positive rotation direction, and when the deviation ΔN is equal to or less than the predetermined value on the negative side, the signal is supplied to the pulse motor 28 in the reverse rotation direction.

The four function generators 101a to 101d provided in the target torque calculating section 101 and the two function generators 7 provided in the engine speed control circuit 70 are provided.
Reference numerals 1 and 72 constitute mode setting means for setting the optimum pump input torque and engine speed according to the work mode. It should be noted that the data stored in advance in each of the above function generators is the same as the above data so that the same amount of work can be obtained when performing normal work regardless of which mode is selected by the mode selection switch 58. The input horsepower of the variable displacement hydraulic pump 1 when switched to the first mode and the input horsepower of the variable displacement hydraulic pump 1 when switched to the second mode are set to be substantially equal. Is preferred.

The operation of the hydraulic construction machine according to this embodiment having the above structure will be described below.

When the mode selection switch 58 is switched to the first mode side suitable for normal work while the engine 27 is started, both the switches 101e and 101f provided in the target torque calculation unit 101 are in contact a. To the side,
From the second function generator 101b to the first function generator 101
The second target torque Tr ₂ larger than the first target torque Tr ₁ set to a is taken out, and the first reference value set to the third function generator 101c from the fourth function generator 101d. The second reference rotational speed Ns _{2 which} is higher than the rotational speed Ns ₁ is taken out. At the same time, the switch 74 provided in the engine speed control circuit 70 is also switched to the contact a side, and the first target set in the first function generator 71 from the second function generator 72. A second target rotational speed Nx ₂ lower than the rotational speed Nx ₁ is taken out.

The target torque calculation unit 101 calculates the target torque command value Tpo from the selected second target torque Tr ₂ and second reference rotation speed Ns ₂ , where Tr ₂ > Tr
_{Since 1} , Ns ₂ > Ns ₁ , there is a large calculated value of Tpo, and therefore the input torque of the variable displacement hydraulic pump 1 becomes large. On the other hand, the engine speed control circuit 70
Calculates the rotation signal of the pulse motor 28 from the second target rotation speed Nx ₂ extracted from the second function generator 72. Since the relationship is Nx ₂ <Nx ₁ , the current governor lever position Nθ is large. In this case, the deviation ΔN of the engine speed is large and has a negative value, and when the deviation ΔN exceeds the dead zone of the third function generator 78, the reverse rotation signal is sent to the pulse motor 28. Is supplied to reduce the engine speed. Further, when the current governor lever position Nθ is small, the deviation ΔN of the engine speed is small, and when the deviation ΔN is a value within the dead zone of the third function generator 78, the engine speed is low. Maintained at rpm. Therefore, the mode becomes a mode suitable for normal work in which the input torque of the variable displacement hydraulic pump 1 is large and the engine speed is low.

On the other hand, the mode selection switch 58 is the second suitable for work requiring a large pump flow rate when the load is low.
When the mode side is switched to the target torque calculation unit 101
Both the switching devices 101e and 101f provided in the first switching device are switched to the contact b side, and the first target torque Tr ₂ smaller than the second target torque Tr ₂ set in the first function generator 101a to the second function generator 101b. While the target torque Tr ₁ is taken out, the third function generator 101c to the fourth function generator 1
The first reference rotation speed Ns ₁ smaller than the second reference rotation speed Ns ₂ set to 01d is taken out. At the same time, the switch 74 provided in the engine speed control circuit 70 is also switched to the contact b side, and the first function generator 71
From the above, the first target rotation speed Nx ₁ higher than the second target rotation speed Nx ₂ set in the second function generator 72 is taken out.

In this case, the target torque command value Tpo calculated by the target torque calculation unit 101 is Tr ₂ > Tr
Mode selection switch 5 from the relation of ₁ , Ns ₂ > Ns ₁
The input torque of the variable displacement hydraulic pump 1 is reduced because the input torque of the variable displacement hydraulic pump 1 is reduced as compared with the case where 8 is switched to the first mode side suitable for normal work. On the other hand, the engine speed control circuit 70 includes a first function generator 71
The rotation signal of the pulse motor 28 is obtained from the target rotation speed Nx ₁ of the above. Since there is a relationship of Nx ₂ <Nx ₁ , when the current governor lever position Nθ is large, the deviation ΔN of the engine rotation speed is small and the deviation ΔN thereof is small. Is the third function generator 7
When the value is within the dead zone of 8, the engine speed is kept at the high speed. Further, when the current governor lever position Nθ is small, the deviation ΔN of the engine speed is large and has a positive value, and when the deviation ΔN exceeds the dead zone of the third function generator 78, A reverse rotation signal is supplied to the pulse motor 28 to increase the engine speed. Therefore, the mode becomes a mode suitable for work requiring a large pump flow rate when the load is small such that the input torque of the variable displacement hydraulic pump 1 is small and the engine speed is high.

Therefore, the hydraulic construction machine of this embodiment is
Without increasing the capacity of the variable displacement pump 1 or setting the engine speed higher during normal work, it is possible to perform crushing work that requires a large amount of pump flow at low load, and it is a multifunctional and high-performance product. The construction machine can be provided at low cost, and the fuel consumption rate during normal work can be reduced, the heat balance can be improved, and noise can be reduced.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIG. The hydraulic construction machine according to the second embodiment is characterized in that the speed sensing characteristic at the time of input torque control is changed according to the governor lever position (target rotation speed; output signal of potentiometer 55).

FIG. 5 is a block diagram of a target torque calculation unit provided in the hydraulic construction machine according to this embodiment. As shown in FIG. 5, the target torque calculation unit 111 of this embodiment has two function generators. It has 111a, 111b, the deviation machine 111c, the correction torque calculation part 111d, and the adder 111e.

The above two function generators 111a and 111b
The governor lever position Nθ detected by the potentiometer 55 is input to each. First function generator 11
1a outputs a target torque Tr having the illustrated characteristics according to the input governor lever position Nθ. On the other hand, the second function generator 111b has the reference rotation speed N having the illustrated characteristics according to the input governor lever position Nθ.
Output s. That is, when the value of the governor lever position Nθ is larger than a predetermined specific value, the target torque Tr output from the first function generator 111a becomes large, and the target torque Tr output from the second function generator 111b becomes large. The reference rotational speed Ns that is set also increases. On the other hand, when the value of the governor lever position Nθ is smaller than a predetermined specific value, the target torque Tr output from the first function generator 111a becomes small and the second function generator The reference rotation speed Ns output from 111b also becomes small.

Therefore, when the value of the governor lever position Nθ is larger than the specific value, the mode selection switch 58 in the hydraulic construction machine of the first embodiment is switched to the first mode side suitable for normal work. As if
Target torque Tp output from target torque calculation unit 111
When o becomes large and the input torque of the variable displacement hydraulic pump 1 becomes large, and conversely the value of the governor lever position Nθ is smaller than the specific value, the mode selection switch 58 in the hydraulic construction machine of the first embodiment. Is switched to the second mode side suitable for work requiring a large pump flow rate when the load is low, the target torque Tpo output from the target torque calculation unit 111 becomes small and the variable displacement hydraulic pump 1 Input torque becomes smaller.

Other parts are configured in the same manner as the device shown in FIGS. 1, 2, and 4 described above. That is, from the engine speed control circuit 70 (see FIG. 4) provided in the controller 50, the mode selection switch 58 is selected.
Is switched to the first mode side suitable for normal work, the second function generator 72 changes the second target speed Nx ₁ lower than the first target rotation speed Nx ₁ set in the first function generator 71. The target speed Nx ₂ is taken out and the engine speed is kept low. On the other hand, when the mode selection switch 58 is switched to the second mode side suitable for work requiring a large pump flow rate at low load such as crushing work, the engine speed control circuit 70 causes the first function generator 71 to operate. The first target rotation speed Nx ₁ higher than the second target rotation speed Nx ₂ set in the second function generator 72 is taken out from, and the engine rotation speed is kept high.

Therefore, by setting the value of the governor lever position Nθ larger than the above specific value and switching the mode selection switch 58 to the first mode side, the input torque of the variable displacement hydraulic pump 1 is large and the engine rotation speed is high. The mode is suitable for normal work, where the number is low. Further, by setting the value of the governor lever position Nθ smaller than the above specific value and switching the mode selection switch 58 to the second mode side, the input torque of the variable displacement hydraulic pump 1 is small and the engine speed is high. That is, the mode becomes a mode suitable for a work requiring a large pump flow rate at a low load, and the same effect as the hydraulic construction machine according to the first embodiment can be obtained.

<Third Embodiment> In this embodiment, as shown in FIG. 6, work detecting means for detecting a work requiring a large amount of pump discharge flow at low load is provided, and the first mode is automatically set. Alternatively, one of the second modes is selected.

The work detecting means uses the pilot pressure supplied to one pilot port 20c of the control valve 20a for controlling the flow of pressure oil to the bucket hydraulic cylinder 21a.
The pressure switch 101 that outputs an ON signal when the value becomes equal to or more than a predetermined value inputs the signal from the pressure switch 101 to the controller 50 instead of the mode selection switch 58. Other than that, the configuration is similar to that of the first embodiment described above. When the pilot pressure of a predetermined value or more is supplied to the pilot port 20c, the control valve 20
6a, the valve position is changed to the left side in FIG. 6, the pressure oil is guided to the bottom side of the bucket hydraulic cylinder 21a, and the bucket (not shown) is operated to the cloud side.

The controller 50 uses the pressure switch 101.
First mode, suitable for normal work, depending on the signal from
Alternatively, the second mode in which a large pump flow rate is required when the load is low is selected, and the corresponding pump input torque and engine speed are output. As described above, at the time of bucket cloud work, a large amount of pump flow rate is usually required to speed up the operation speed even with a low load, and the controller 50 causes the second pressure switch 101 to turn on when the signal from the pressure switch 101 is on. If the mode is OFF, the first mode is selected. Therefore, the same effects as those of the hydraulic construction machine according to the first and second embodiments can be automatically exhibited.

[0052]

As described above, according to the present invention,
The first mode that combines a low engine speed and a large pump input torque is assigned during normal work, and a high engine speed and a small pump input torque are assigned during crushing work that requires a large pump flow rate at low load. Since the engine speed and the pump input torque are controlled by allocating the second mode in which the variable speed pump is combined, the variable displacement pump is not increased in capacity, and the engine speed during normal work is not set to be high, and Work such as crushing that requires a large amount of pump flow during loading can be performed. Therefore, it is possible to provide a multifunctional and high-performance construction machine at low cost, improve the fuel consumption rate during normal work, and reduce the heat radiation to the engine cooling water as the fuel consumption rate improves. In addition, the heat balance can be improved, and the noise can be reduced as the engine speed is reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a hydraulic construction machine according to a first embodiment.

FIG. 2 is a circuit diagram of a tilt angle control circuit provided in the hydraulic construction machine according to the first embodiment.

FIG. 3 is a circuit diagram of a target torque calculation unit according to the first embodiment.

FIG. 4 is a circuit diagram of an engine speed control circuit provided in the hydraulic construction machine according to the first embodiment.

FIG. 5 is a circuit diagram of a target torque calculation unit according to the second embodiment.

FIG. 6 is a configuration diagram of a hydraulic construction machine according to a third embodiment.

FIG. 7 is a characteristic diagram of an engine mounted on a hydraulic construction machine.

FIG. 8 is a characteristic diagram of a variable displacement hydraulic pump mounted on a hydraulic construction machine.

[Explanation of symbols]

 1 Variable Capacity Hydraulic Pump 4,21 Actuator 27 Engine 27a Governor 27b Governor Lever 40 Tilt Angle Control Device 44 Regulator 50 Controller 55 Mode Selection Switch 60 Tilt Angle Control Circuit 70 Engine Speed Control Circuit 71, 72, 78 Function Generator 74 Switching device 77 Deviation device 100 Torque control unit 101 Target torque calculation unit 101a to 101d Function generators 101e, 101f Switching device 101g Deviation device 101h Correction torque calculation unit 101i Adder

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Claims (9)

[Claims] 1. An engine, a rotation control device for controlling a rotation speed of the engine, a variable displacement hydraulic pump driven by the engine, a regulator for setting an input torque of the variable displacement hydraulic pump, and the variable displacement. In a hydraulic construction machine including an actuator driven by pressure oil discharged from a displacement hydraulic pump, a first mode in which a first engine speed and a first pump input torque are combined is set, and Mode setting means for setting a second mode in which a second engine rotation speed higher than the first engine rotation speed and a second pump input torque smaller than the first pump input torque are set, and the mode. The first mode or the second mode set in the setting means is selected, and the engine speed signal and the pump according to the selected mode are selected. Hydraulic construction machine characterized by comprising a mode selection means for outputting an input torque signal. 2. The hydraulic construction machine according to claim 1, wherein the mode selection means selects the second mode when performing work requiring a large pump discharge flow rate at a low load, and A hydraulic construction machine characterized by selecting the first mode during normal work other than the above. 3. The hydraulic construction machine according to claim 2, further comprising work detecting means for detecting a work requiring a large amount of pump discharge when the load is low, and the mode selecting means is a signal from the work detecting means. A hydraulic construction machine, characterized in that either the first mode or the second mode is selected in accordance with the above. 4. The hydraulic construction machine according to claim 1 or 2, further comprising a mode selection switch operated by an operator, wherein the mode selection means responds to a signal from the mode selection switch. Alternatively, the hydraulic construction machine is characterized in that either one of the second modes is selected. 5. The hydraulic construction machine according to claim 1, further comprising: a unit for setting a target engine speed of the engine and a target engine speed setting unit for detecting an operation amount of the target engine speed setting unit. A hydraulic construction characterized in that a manipulated variable detecting means is provided, and the engine speed is controlled in accordance with each of the characteristics corresponding to the first mode or the second mode according to the manipulated variable detection signal. machine. 6. The hydraulic construction machine according to any one of claims 1 to 5, further comprising a target rotation speed detecting means for detecting a target rotation speed of the engine, and an actual rotation speed detecting means for detecting an actual engine rotation speed. And a correction means for correcting the pump input torque in accordance with the rotation speed deviation between the target rotation speed and the actual rotation speed, and corresponding to the first mode or the second mode, the pump input torque A hydraulic construction machine characterized by changing a correction amount. 7. The hydraulic construction machine according to claim 6, wherein in the mode setting means, in both the first mode and the second mode, the target rotation speed of the engine is equal to or more than a predetermined rotation speed. A hydraulic construction machine characterized in that the pump input torque is set to be small. 8. The hydraulic construction machine according to claim 6 or 7, wherein the pump input torque is set in the mode setting means within a range not exceeding an output torque of the engine corresponding to a target rotation speed of the engine. A hydraulic construction machine characterized by that. 9. The hydraulic construction machine according to claim 1, wherein the mode setting means has an input horsepower of the variable displacement hydraulic pump when the first mode is selected, and A hydraulic construction machine, wherein the engine speed and the pump input torque are set so that the input horsepower of the variable displacement hydraulic pump when the second mode is selected becomes substantially equal.